Upgrades rarely fail in the moment. They fail later when drift accumulates—old services, misaligned config, or disk creep. This guide explains the mindset and follow-up that keeps things stable.
Common post-upgrade drift
- Old services still running or failed units not restarted
- Config files not aligned with new versions
- Disk usage creeping up from leftover packages or logs
Fix mindset
- Verify services (Apache, PHP-FPM, key sites)
- Validate versions (PHP, pools, vhosts)
- Clean up leftovers: Ubuntu upgrade cleanup
FAQ
What’s the first thing to run after an apt upgrade?
sudo systemctl --failed --no-pager to see failed units, then df -h to check disk. Run post-upgrade cleanup and routine service health checks.
We have multiple PHP versions; could that be part of it?
Yes. Mixed versions and pool mix-ups are a common source of “it worked before the upgrade.” See PHP version drift on multi-site servers.
Related
- Ubuntu upgrade cleanup checklist — cleanup steps
- PHP version drift on multi-site servers — version and pool drift
- Routine service health checks for WordPress servers — quick verification